Fuel Pressure VSV Delete

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Aug 18, 2017
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Has anyone deleted their fuel pressure VSV on the 1FZ, and just run a vacuum line straight from the intake manifold directly to the fuel pressure regulator (FPR)?





I understand that the VSV is designed to control vacuum to the FPR under certain conditions (hot starting? cold starting? high vacuum?). Several other Toyota guys have deleted this system entirely to simplify the vacuum routing and the fuel system. Just curious if anyone has done it on a FZJ80 and what their experience has been.

Thanks!

p1020567
 
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On the 3FE, it is there to increase fuel pressure during cranking to aid in starting, and for a short while after engine start. Many bypass it without adverse effects, including myself. 1FZ may be similar.
 
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On the 3FE, it is there to increase fuel pressure during cranking to aid in starting, and for a short while after engine start. Many bypass it without adverse effects, including myself. 1FZ may be similar.
Awesome. Thanks for the intel.
 

Proven

RTFM, STEP 6, POST
 
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It is getting closer that mine will be outside the Georgia inspection range and I'd like to eliminate the EGR and as much of these systems as possible in my 1996.

The fewer systems that could fail, the better.
 

inkpot

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It is getting closer that mine will be outside the Georgia inspection range and I'd like to eliminate the EGR and as much of these systems as possible in my 1996.

The fewer systems that could fail, the better.
Only take about 30 minutes to fabricate an EGR blockoff plate and install it between the riser tube and the upper intake. Exhaust gas no longer moves thru the EGR tube making it stay much cooler. This is only hearsay, as I would never delete a federally mandated emission system.
 

inkpot

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So, other than simplifying the system and reducing the chances of additional system failures as these rigs age, is there any benefit to running 100% fuel pressure all the time? Does it make you go any faster? On the other hand, does it fatigue the injectors prematurely?
 
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The fuel pressure increase is only during cranking.

At all other times, the fuel pressure is modulated by manifold vacuum to the FPR, so at low loads the fuel pressure will be lower. Tampering with THAT system causes rough running and black smoke from over-fueling. We are talking only about the VSV that activates during cranking to boost the pressure.
 
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speaking of FPR mine sounds like it has an air leak when i just turn on the ignition,no cranking,sounds like a slight hissing noise.
is this normal?
 
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Considering that is a pic of my trucks engine you used, yes it has been fine , toss all that stuff
Yessir! We spoke about it via PM. I was just trying to get a larger sample size. Thanks for your help!
 
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Joined
Aug 18, 2017
Messages
876
Location
Austin, TX
The fuel pressure increase is only during cranking.

At all other times, the fuel pressure is modulated by manifold vacuum to the FPR, so at low loads the fuel pressure will be lower. Tampering with THAT system causes rough running and black smoke from over-fueling. We are talking only about the VSV that activates during cranking to boost the pressure.
Great intel. Thx!
 

landtank

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that VSV is there to increase the fuel pressure during hot starts so as to add more fuel. It does this by closing the FPR off from the intake vacuum. On a regular basis vacuum is always present and the fuel pressure is regulated to provide a constant pressure differential between the fuel and intake which provides a consistent delivery of fuel and spray pattern. No reason to gut the system unless removing beneficial systems are your thing.
 
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that VSV is there to increase the fuel pressure during hot starts so as to add more fuel. It does this by closing the FPR off from the intake vacuum. On a regular basis vacuum is always present and the fuel pressure is regulated to provide a constant pressure differential between the fuel and intake which provides a consistent delivery of fuel and spray pattern.
Thank you for the explanation! I knew the VSV functioned under a certain scenario, but I wasn’t exactly sure when.
 
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I removed everyone of the switches under there. Mine is obd1 and runs just fine.
Awesome, that's my plan. And I'm going to weld all of the extra vacuum ports closed.
@slow95z & @Will Van :

By "every one of the switches" do you literally mean EVERYTHING that's running on vacuum?
Did y'all remove every VSV, every check valve, & every single vacuum line?
Basically everything pointed out and bolded on page EG-172 in the FSM?

I'm having serious idling issues with my new to me FZJ80 with OBD1. The previous owner removed the EGR, PAIR, and some vacuum lines are removed/capped off. But I'm not entirely sure what's causing my issues. I replaced the O2 sensors and spark plugs and things seemed to have only worsened.


A few quirks I'm experiencing though:
Until the engine is completely warmed up the engine basically refuses to go beyond 1200 RPM while in Drive. In neutral or park it will slowly increase however high I want it to go, but not in Drive, even with the pedal to the floor.

Additionally, this morning, for the first time, the power steering seemed non-existent at first, then slowly built up to normal when pulling out of my parking garage. And my brakes seemed to not function when I was reversing out of my parking spot as well. I quickly popped it from reverse to neutral and then the brakes seemed to function normally, and were fine after that.
 
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